body {
  padding: 0;
  margin: 0; 
}

.nav-bar {
  display: flex;
}

.nav-item {
    height: 44px;
    line-height: 44px;
    text-align: center;
}

.nav-left , .nav-right {
  height: 44px;
  width: 70px;
  background-color: red;
}

.nav-center{
  flex: 1;
  height: 44px;
  background-color: blue;
}
